.tab ul {
  overflow: hidden;
  padding: 0;
  margin: 0;
}
.tab ul li {
  box-sizing: border-box;
  padding: 0;
  float: left;
  width: 100px;
  height: 45px;
  line-height: 45px;
  list-style: none;
  text-align: center;
  border-top: 1px solid blue;
  border-right: 1px solid blue;
  /* 鼠标手型样式 */
  cursor: pointer;
}
.tab ul li:first-child {
  border-left: 1px solid blue;
}
.tab ul li.active {
  background-color: orange;
}
.tab div {
  width: 500px;
  height: 300px;
  /* 隐藏 */
  display: none;
  text-align: center;
  font-size: 30px;
  line-height: 300px;
  border: 1px solid blue;
  border-top: 0px;
}
.tab div.current {
  /* 显示 */
  display: block;
}
